1. Field of the Invention
The present invention relates to a switch unit and a vehicle mounted device control apparatus using this switch unit, and more particularly to a structure of a switch unit in which switching functions are alterable properly, and to a vehicle mounted device control apparatus which, when this type of switch unit is mounted in a unit mounting section, automatically makes a decision on the type of switching function of the mounted switch unit.
2. Description of the Related Art
In conventional motor vehicles, a plurality of manual switches are disposed on a panel surface of an instrument panel for controlling air conditioning in the interior of a room so that selective operation of any one of these manual switches performs switching between heating and cooling for the interior of the room or alteration of a set value of the in-room temperature.
Recently, in addition to the foregoing group of manual switches for air conditioning, for meeting a variety of user""s options, there has been a request to place one or a plurality of optional manual switches for operations of optionally equipped devices on the surface of the instrument panel. Accordingly, so far, a switch apparatus has been proposed, which is capable of disposing a plurality of optional manual switches different in kind from each other.
This type of switch apparatus, proposed so far, has a unit mounting section which permits the mounting of a plurality of switch units provided with optional manual switches so that one switch unit or a plurality of switch units different in kinds from each other are mounted arbitrarily on the unit mounting section. Even in a case in which any kind of switch unit is mounted thereon, a control section (CPU) of a control device processes a switching signal from that switching unit to fulfill the function of that switching unit.
Furthermore, of such kinds of well-known switch apparatus, there has been known a vehicle mounted device control apparatus which, when a switch unit is mounted in the unit mounting section, performs a function to automatically make a decision as to the kind of that switch unit, one example of which is a switch apparatus disclosed in U.S. Pat. No. 5,811,891.
The switch apparatus, disclosed in U.S. Pat. No. 5,811,891, is composed of a plurality of kinds of switch units, a control device for selectively putting these switch units in a unit mounting section, and a control circuit unit built in the control device. In addition, on the switch unit side, a recognition signal issuing means is provided for generating a recognition signal peculiar to that switch unit while, on the control circuit unit side, a switch decision circuit is provided which, upon receipt of the recognition signal, generates a drive signal for driving a predetermined load. The recognition signal issuing means has internal wiring varying according to the kinds of switch units to, in response to operation (turning-on) of switches of the switch unit, output different recognition signals (switch signals). The switch decision circuit includes a plurality of logic circuits, a plurality of input terminals and a plurality of output terminals. This switch decision circuit is for, when a recognition signal (switch signal) is supplied from the mounted switch unit to any one of the plurality of input terminals, generating a drive signal to be given to a load corresponding to the function of the switch unit mounted on any one of the output terminals, in accordance with the polarity or the like of the recognition signal supplied input terminal and the supplied recognition signal (switch signal).
According to the switch apparatus disclosed in U.S. Pat. No. 5,811,891, a desired kind of switch unit is mounted in the unit mounting section of the control circuit unit and, when a switch of the switch unit is turned on, the switch unit generates a recognition signal peculiar to its function to supply the recognition signal to the switch decision circuit of the control circuit unit, while the switch decision circuit receives the recognition signal to make a decision on the kind of the mounted switch unit on the basis of the received recognition signal. Thus, only with the replacement of the switch unit to be mounted in the unit mounting section, it is possible to automatically make a decision about the switch units having various functions and to conduct operations corresponding to the functions of the switch units.
Meanwhile, although the switch apparatus disclosed in U.S. Pat. No. 5,811,891 can automatically make a decision on the kind of each of switch units having various functions and conduct an operation corresponding to the function of the switch unit only with the switch unit being mounted in the unit mounting section of the control circuit unit, in this switch apparatus, the switch unit side requires internal wiring with switches varying according to the kind of switch unit for the decision on the function of the switch unit, and the control circuit unit side requires installation of a switch decision circuit including a plurality of logic circuits, a plurality of input terminals and a plurality of output terminals.
From this point of view, in the case of the switch apparatus disclosed in U.S. Pat. No. 5,811,891, not only the switch unit decision means becomes complicated so that the manufacturing cost of the control circuit unit becomes high accordingly, but also the kinds of switch units are limited in number because limitation is imposed on combinations of the logic circuits.
For solving such problems, Japanese Patent Application No. 8-166237, already filed by the same applicant, discloses a vehicle mounted device control apparatus capable of making a decision about the functions of switch units including switches, variable resistors, and other components with an extremely simple structure without increasing the manufacturing cost.
Furthermore, in a vehicle mounted device control apparatus disclosed in U.S. Pat. No. 5,990,571, resistive elements are principally used in a switch unit to divide an analog voltage, inputted to the switch unit, with these resistive elements, and the divided analog voltages are analog/digital-converted and then processed in an CPU (control section).
Thus, in this vehicle mounted device control apparatus disclosed in U.S. Pat. No. 5,990,571, since the analog-to-digital conversion processing takes time, new problems arise, for example, in that difficulty is encountered in increasing the processing speed to a high value and in providing a high reliability because of noise superimposed at the analog voltage circuit section.
Accordingly, it is an object of the present invention to provide a vehicle mounted device control apparatus capable of making a decision about the kinds of switch units with an extremely simple structure without increasing the manufacturing cost, and further capable of conducting processing at a high speed and with high reliability, and to provide a switch unit suitable for use in the vehicle mounted device control apparatus.
For achieving this purpose, in accordance with this invention, there is provided a switch unit comprising a circuit substrate having a required circuit pattern formed to include a plurality of pairs of short-circuiting possible land portions, and a switch mounted on the circuit substrate, wherein any one of the plurality of pairs of land portions are short-circuited selectively to set a switching function of the switch.
In addition, according to this invention, a display for showing the switching function of the switch can be provided on an outer surface of each of key tops for manipulating the switch, and this display can be of a transmission type making transmission of light from an light-emitting diode installed in the switch unit.
The foregoing means permits a circuit pattern to be formed on a circuit substrate to be used in common to various switch units different in type of switching function from each other, and a switch unit having a required switching function is attainable only in a manner that predetermined land portions are short-circuited through the use of a jumper chip or the like. Accordingly, it is possible to manufacture various switch units having different types of switching function from each other at a low cost, which contributes to a drop in the manufacturing cost of a vehicle mounted device control apparatus equipped with these switch units.
Moreover, in accordance with this invention, there is provided a vehicle mounted device control apparatus comprising a plurality of unit mounting sections each for accepting a switch unit which includes a circuit substrate having a required circuit pattern formed to contain a plurality of pairs of short-circuiting possible land portions and a switch, mounted on the circuit substrate, so that any one of the plurality of pairs of land portions are short-circuited selectively to set a switching function of the switch, and a switch unit decision section for, when the switch unit is mounted in one of the plurality of unit mounting sections, detecting the land portions short-circuited to automatically make a decision about a kind of the switching function of the mounted switch unit.
The means for detecting the short-circuited land portions can be a means in which the switch is connected between the land portion of the circuit pattern and a ground terminal. In this case, when the switch is turned on, since the voltage of an output terminal connected to the short-circuited land portions drops selectively to the ground voltage, the switch unit decision section can recognize the output terminal of the switch unit in which the voltage has dropped to the ground voltage, which enables the decision of the kind of the switch unit. Incidentally, for facilitating an electrical connection between the output terminal of the switch unit and the switch unit decision section, they can be connected through a connector to each other.
With the foregoing means, only in a manner that a plurality of pairs of short-circuiting possible land portions are provided simply on the switch unit side and the land portions predetermined according to the kind of the switching function of each switch unit are short-circuited selectively, the switch unit decision section side can automatically make a decision about the kind of each switch unit mounted in the unit mounting section. This can simplify the circuit arrangement of the vehicle mounted device control apparatus and perform the function thereof at a low cost. Additionally, since the detection of the short-circuited land portions, that is, the decision about the kind of the switching function of each switch unit, can be made through digital processing, the decision processing can be made at a high speed, and have a high resistance to noise.